System for producing expanded tobacco

ABSTRACT

A system for producing expanded tobacco, comprises a tobacco expansion apparatus, in which the tobacco is expanded, at least a first tobacco supply unit for providing tobacco containing at least one suitable chemical solvent other than water to prepare the tobacco for expansion, at least a second tobacco supply unit for providing tobacco containing only water as a solvent to prepare the tobacco for expansion and at least a first feed unit for introducing tobacco from the at least first tobacco supply unit and the at least second tobacco supply unit into the tobacco expansion apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to EuropeanApplication No. 06405497.6, filed Nov. 23, 2006, the entire content ofwhich is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a system for producing expandedtobacco.

BACKGROUND

Various processes and systems for producing expanded tobacco are knownin the art. Typically, the tobacco is treated before expansion, eitheronly with water or with additional chemical solvents, for example liquidor gaseous carbon dioxide, nitrogen or iso-pentane or other suitablesolvents in gaseous or liquid form. Typical expansion rates of tobaccotreated only with water are in the range of from about 5 percent toabout 15 percent. Typical expansion rates of tobacco treated withadditional chemical solvents may be in the range of from about 80percent to about 120 percent.

The systems for expanding tobacco known in the art comprise a supplyunit of tobacco, an expansion apparatus and a feed unit that feeds thetobacco from the supply unit into the expansion apparatus. The supplyunit may comprise a treatment unit where the tobacco is treated toprepare the tobacco for expansion. These systems are for example knownfrom U.S. Pat. No. 4,340,073 or U.S. Pat. No. 4,407,306. Once a systemto expand tobacco is set up, the process of treating and expandingtobacco is fixed within narrow boundaries. The tobacco expansionapparatus can thus only expand tobacco which has been treated by thepre-selected specific process. Therefore the systems to expand tobaccoare currently not flexible.

SUMMARY

The present invention provides a system for producing expanded tobaccocomprising at least a first tobacco supply unit for providing tobaccocontaining at least one suitable chemical solvent other than water toprepare the tobacco for expansion and at least a second tobacco supplyunit for providing tobacco containing only water as a solvent to preparethe tobacco for expansion. The system for producing expanded tobaccofurther comprises a tobacco expansion apparatus and at least one feedunit. The feed unit is configured to introduce the tobacco into thetobacco expansion apparatus from the at least first tobacco supply unitor the at least second tobacco supply unit. Additionally, the feed unitmay feed tobacco simultaneously from the first or the second supplyunit.

The term “tobacco” is used throughout the specification to encompass allparts of any tobacco plant, treated or untreated, that are expandable.In particular, the term tobacco refers to cut or shredded tobacco. It isalso meant to include other parts of the tobacco plant, for examplestems or pre-treated tobacco, for example flavoured cut tobacco.

The term “chemical expansion” is used throughout the specification torefer to any process of expanding tobacco containing an additionalsuitable chemical solvent other than water to prepare the tobacco forexpansion.

The term “tower drying” is used throughout the specification to refer toany process of expanding tobacco containing only water as a solvent toprepare the tobacco for expansion.

The term “chemical solvent” is used throughout the specification torefer to any substance which is suitable to enhance the expansion of thetobacco inside the tobacco expanding apparatus, for example liquid orgaseous carbon dioxide, nitrogen or iso-pentane or other suitablesolvents in gaseous or liquid form.

In an alternative embodiment of the system according to the inventionthe system comprises at least two feed units. Each feed unit isconfigured to feed tobacco from either one of the supply units to thetobacco expansion apparatus. For this purpose the tobacco expansionapparatus has two separate entries for the introduction of the tobacco.

In a further embodiment of the system according to the invention, morethan two feed units are used to feed the tobacco from more than twosupply units into the tobacco expansion apparatus at one or severallocations. Preferably some of the supply units contain tobacco which hasbeen treated by a different treatment process.

Accordingly, the same system according to the invention allows theexpansion of tobacco that has been treated in different ways tofacilitate expansion, that is, tobacco treated with water as a solventand tobacco treated with at least an additional chemical solvent. Theexpansion apparatus is then operated with process parameters suited tothe specific type of pre-treatment of the tobacco. In addition, thesystem allows combinations of both types of processes to be performed.Accordingly, substantial investments can be saved, since the system canbe used for both types of processes, requiring only one tobaccoexpansion apparatus.

Accordingly, products which are produced using chemical expansion can beproduced in the same system as products which are produced using towerdrying. This allows using production capacities for chemical expansionsystems which may otherwise be unused. The same holds for productioncapacities for tower drying.

It is also possible to upgrade either an existing chemical expansionsystem or an existing tower drying system with an additional supply unitof the other type at a considerable lower cost than a complete newinstallation would require.

Also, since it is possible to combine tower drying and chemicalexpansion in one system it is now possible to produce tobacco blendswhich are typically produced using chemical expansion technology atfinal moisture levels in the range of from about 8 percent to about 15percent without the need of subsequent remoistening. This process stepof remoistening, which is common in tobacco expansion, is often referredto in the art as “reordering”. Expanded tobacco which has been producedusing chemical expansion typically has a moisture content in the rangeof from about 2 percent to about 5 percent when leaving the tobaccoexpansion apparatus. This is considered as too low for furtherprocessing. Therefore, up to now in a subsequent reordering step theexpanded tobacco has been moisturized to achieve a moisture content oftypically about 11 percent. Nonetheless, with the system according tothe invention also expanded tobacco with a moisture level between about2 percent to about 8 percent may be produced, requiring partialreordering afterwards.

On the other hand it is possible with the system according to theinvention to produce a superior quality of expanded tobacco in terms ofexpansion rate of a water solvent expanded product by lowering themoisture of the tobacco leaving the tobacco expansion apparatus belowtypical tower dryer conditions. For example moisture levels in the rangefrom about 2 percent to about 15 percent may be achieved. The tobaccopre-treated with water for expansion may be exposed to the processparameters normally used for chemical expansion of tobacco. This resultsin a greater expansion rate and a reduced moisture level compared toconventional tower drying.

An additional advantage of the system according to the invention is thatthe combination of the chemical expansion with the tower drying reducesthe fire risk in the tobacco expansion apparatus. The fire risk isreduced when the conditions of tower drying heat treatment are appliedfor chemical expansion, as the tower drying process runs at a lowertemperature as the chemical expansion.

Optionally, in a preferred embodiment of the system the tobaccoexpansion apparatus comprises an expansion tower dryer.

Also, optionally, in a preferred system according to the invention theapparatus for providing the tobacco treated for expansion with at leastone chemical solvent other than water comprises an impregnator where thetobacco is exposed to the chemical solvent, for example carbon dioxide.In the impregnator, the tobacco is exposed to liquid carbon dioxide, sothat the tobacco is soaked. Alternatively, the chemical solvent to whichthe tobacco is exposed in the impregnator is gaseous carbon dioxide.This is possible for tobacco that has been cooled to a temperature belowthe temperature of the pressurized gaseous carbon dioxide which is at ornear saturation. Then controlled condensation of carbon dioxide on thetobacco occurs and the tobacco gets soaked.

In a further embodiment of the system according to the invention, theapparatus for providing the tobacco containing water as a solventcomprises a silo for storing the tobacco. The silo has an outlet and adetangling unit for detangling the shreds of tobacco is arranged in thesilo. Usually the silos for the tobacco are equipped with large slowmoving doffers to feed tobacco from the entire height of the silo to theoutlet of the silo. Depending on the moisture content of tobacco,tobacco may tend to form pads and clumps at the exit of the storagesilos. The higher the moisture content, the more the tobacco tends toform pads and clumps. Such pads and clumps may have an adverse effect ontower drying systems, since they may cause blockage at the feed unitwhere the tobacco is introduced into the stream of process gas, forexample superheated steam. As a consequence, this may lead tonon-uniform heat treatment which may adversely affect the quality of theexpanded tobacco.

While it is known to provide a detangling unit with a small number ofdoffers, for example two to five doffers between the outlet of a siloand the tobacco expansion apparatus, this separate detangling unitrequires additional space. Also, due to the small number of doffers andthe short residence time of the tobacco in the detangling unit, thesedoffers have to rotate with a comparatively high speed, for example witha speed of 100 rotations per minute and more. Accordingly, the tobaccois subjected to substantial mechanical stress which may result insubstantial tobacco degradation.

Advantageously, in the system according to the invention the detanglingunit comprise a plurality of slowly rotating short doffers which arearranged essentially over the entire width and height of the silo. Dueto the larger number of doffers a high speed for detangling is notrequired and thus, the tobacco is slowly detangled and degradation ofthe tobacco is significantly reduced. Also, the detangling is performedin the silo thus eliminating the need for any additional space.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous aspects of the invention will become apparent fromthe following description of preferred embodiments of the invention withthe aid of the drawings, in which:

FIG. 1 a is a schematic representation of a first embodiment of a systemfor producing expanded tobacco in accordance with the invention,

FIG. 1 b is a schematic representation of a second embodiment of asystem for producing expanded tobacco in accordance with the invention,and

FIG. 2 is a schematic representation of a silo comprising a detanglingunit.

DETAILED DESCRIPTION

FIG. 1 a shows a schematic representation of a first embodiment of asystem for producing expanded tobacco according to the invention. Theshown embodiment of the system comprises a feed unit 10 for introducingtobacco into a tobacco expansion apparatus comprising a tower dryer 20.The tower dryer 20 is connected to a conduit 21 through which a streamof process gas flows during operation. The process gas may be, forexample, hot air or superheated steam. The upper end of the tower dryer20 opens out into a tangential separator 22. Alternatively, a cyclonemay be used to separate the expanded tobacco from the process gas.During operation the stream of process gas carrying the tobacco isseparated from the tobacco in the tangential separator. The tobaccodischarges at the bottom of the tangential separator 22. The process gasis further processed, for example cleaned and reheated, and thenreintroduced into the conduit 21.

A first supply unit 30 for providing the treated tobacco comprises asilo 40, an impregnator 31 and a vibrating silo 33. The clump breaker 32is optional and typically used only for a liquid carbon dioxideimpregnation of the tobacco.

A second supply unit 35 for providing the tobacco containing water as asolvent comprises a silo 40 in which a detangling unit 400 is arranged.Both supply units 30, 35 may share the same silo 40. Alternatively,different silos 40 may be provided for tobacco to be expanded usingchemical expansion and for tobacco to be expanded using tower drying.This may be especially useful since the moisture content of the tobaccoto be expanded using chemical expansion typically is different from themoisture content of the tobacco to be expanded using tower drying. Onthe other hand, the moisture content of the tobacco from any one of thesupply units 30, 35 may be changed after leaving the silo 40, as well.

The detangling unit 400 arranged in the silo 40 is schematicallyrepresented in FIG. 2. The detangling unit 400 comprises a number ofsmall doffers 401, which are arranged in the silo essentially over theentire width and height of the silo 40. In FIG. 2, only some smalldoffers 401 are shown. The small arrows indicate the respectivedirection of rotation of the small doffers 401 during operation. Sincethe doffers 401 are arranged over the entire width and height of thesilo 40 they need to rotate only slowly compared to the doffers of thedetangling units according to the state of the art. Due to thecontinuous and careful detangling of the shreds of tobacco in the silo,tobacco degradation is substantially reduced if not completely avoided.Since the detangling unit is completely arranged in the silo 40, noadditional space is needed.

The feed unit 10 comprises means to advance the tobacco to the entrysection 210 of the conduit 21 of the tobacco expansion apparatus 20.

The tobacco is introduced into the stream of hot air at the entrysection 210 of the conduit 21. A stream 23 of hot air loaded withtobacco then flows through the tower 20 and discharges into thetangential separator 22. The entry section 210 may include a rotaryvalve and a Venturi type nozzle.

In an alternative embodiment shown in FIG. 1 b the system according tothe invention comprises also a second feed unit 11. In this embodimenteach feed unit 10, 11 is dedicated to a supply unit 30, 35 and feedsinto a separate entry of the conduit 21.

The described embodiment of the system according to the invention worksessentially as follows for chemical expansion. In the first supply unit30 tobacco is introduced from the silo 40 into the impregnator 31. Theimpregnator 31 is then closed and purged with gaseous carbon dioxide toremove the air from the impregnator 31. The impregnator 31 is thenpressurized for example at 30 bar, at the same time cooling the tobaccoto about minus 10 degrees Celsius. Then the tobacco is soaked by liquidcarbon dioxide. When the impregnator 31 is depressurized carbon dioxidehydrates are formed which act as a puffing agent of the tobacco. Thedepressurization cools the tobacco to about minus 80 degrees Celsius.Excessive carbon dioxide that has remained in the impregnator 31 upondepressurization forms dry ice. For this reason tobacco expanded by thisprocess is sometimes referred to as dried ice expanded tobacco.

The thus treated tobacco leaves the impregnator 31 and enters the clumpbreaker 32 to break any clumps that may have formed. The tobacco thenenters the vibrating silo 33 to achieve an essentially continuous flowof tobacco towards the first feed unit 10. In an alternative methodtobacco is treated by gaseous carbon dioxide instead of liquid carbondioxide. In this method no clumps are formed and accordingly the clumpbreaker 32 is not necessary.

The impregnated tobacco is now introduced into a stream of hot airflowing through the conduit 21, for example at the entry section 210 ofconduit 21. To produce a negative pressure at the entry section 210 ofthe conduit a Venturi nozzle may be used. This avoids expansion of thetreated tobacco before the tobacco expansion apparatus 20.

The hot air which is typically at a temperature in the range of from 300degrees Celsius to 380 degrees Celsius causes the tobacco to beexpanded. The stream of hot air 23 carrying the expanded tobacco is thendischarged into the tangential separator 22, at the outlet of which theexpanded tobacco can be recollected.

Among the parameters that affect the expansion rate of the tobacco arethe impregnation solvent, the load of the tobacco expansion apparatus,the steam concentration in the conduit 21, the process gas velocity andthe temperature of the process gas.

It is also possible to perform this type of process using chemicalsolvents other than carbon dioxide, for example nitrogen or iso-pentaneor other suitable solvents. Also, it is possible to introduce thechemical solvent to the impregnator 31 either in liquid or in gaseousform in order to soak the tobacco with the solvent.

When leaving the tobacco expansion apparatus 20 expanded tobacco whichhas been produced using only the afore-described chemical expansiontechnology typically has a moisture content which is in the range offrom about 2 percent to about 5 percent. However, this moisture contentis considered too low for further processing. Therefore, the expandedtobacco is typically moisturized in a subsequent reordering step (notshown in the drawings) to achieve a final moisture content for theprocessed tobacco of typically about 11 percent.

In the tower drying process the tobacco is removed from the silo 40 withthe aid of the small doffers 401 of the detangling unit 400.Substantially pad-free and clump free tobacco is forwarded to the firstfeed unit 10, or, if two feed units 10, 11 are used to second feed unit11, so that no blockage occurs at the second feed unit 11. The tobaccois then introduced into a stream of non-saturated superheated steam,which may typically have a temperature in a range of about 180 degreesCelsius to about 400 degrees Celsius, preferably between about 180degrees Celsius to about 250 degrees Celsius. The speed of the stream ofsuperheated steam typically may be within the speed range of from about18 meters per second to about 25 meters per second. The moisture contentof the tobacco in the silo 40 typically may be within the range of fromabout 20 percent to about 32 percent. The moisture content of thetobacco when recollected from the tangential separator 22 typically maybe within the range of from about 11 percent to about 14 percent.

Up to today, it has not been possible to use the same system forchemical expansion and tower drying, since the respective systems werespecifically designed for one type of process. Now, the combination ofthe two types of processes (chemical expansion and tower drying) is alsopossible with the system according to the invention. Furthermore it ispossible, for example, to introduce tobacco treated with a chemicalsolvent into a stream of superheated steam. This allows producingexpanded tobacco having virtually any moisture content between about 8percent to about 15 percent without the need of subsequent complete orpartial reordering of the expanded tobacco. Alternatively expandedtobacco with a moisture content between about 2 percent and about 8percent may be produced which is then completely or partially reordered.Accordingly, the system of the invention allows producing expandedtobacco by using only tower drying, only chemical expansion, and anycombinations thereof to achieve any desired final tobacco moisturecontents within predetermined ranges, and corresponding expansion rates.Also, the system allows the use of capacities for one type of processwhich would remain otherwise unused, or it avoids additional investmentsin a system for the respective other type of process. Also, since thesystem allows combinations of the described types of processes to beperformed, it may substantially reduce the fire risk when tower dryingheat treatment conditions are applied to tobacco treated with a chemicalsolvent for the expansion.

1. A system for producing expanded tobacco, comprising a tobaccoexpansion apparatus, in which the tobacco is expanded, at least a firsttobacco supply unit for providing tobacco containing at least onesuitable chemical solvent other than water to prepare the tobacco forexpansion, at least a second tobacco supply unit for providing tobaccocontaining only water as a solvent to prepare the tobacco for expansionand at least a first feed unit for introducing tobacco from the at leastfirst tobacco supply unit and the at least second tobacco supply unitinto the tobacco expansion apparatus.
 2. A system for producing expandedtobacco, comprising a tobacco expansion apparatus, in which the tobaccois expanded, at least a first tobacco supply unit for providing tobaccocontaining at least one suitable chemical solvent other than water toprepare the tobacco for expansion, at least a second tobacco supply unitfor providing tobacco containing only water as a solvent to prepare thetobacco for expansion, at least a first feed unit for introducingtobacco from the at least first tobacco supply unit into the tobaccoexpansion apparatus, and at least a second feed unit for introducingtobacco from the at least second tobacco supply unit into the tobaccoexpansion apparatus.
 3. A system according to claim 1, wherein thetobacco expansion apparatus comprises a tower.
 4. A system according toclaim 1, wherein the at least a first supply unit for providing thetobacco containing a chemical solvent other than water comprises animpregnator where the tobacco is exposed to liquid or gaseous carbondioxide.
 5. A system according to claim 1, wherein the at least a secondsupply unit for providing the tobacco containing water as a solventcomprises a silo for storing the tobacco, the silo having an outlet,with a detangling unit for detangling the shreds of tobacco beingarranged in the silo.
 6. A system according to claim 5, wherein thedetangling unit comprises a plurality of slowly rotating small dofferswhich are arranged essentially over the entire width and height of thesilo.
 7. A system according to claim 2, wherein the tobacco expansionapparatus comprises a tower.
 8. A system according to claim 2, whereinthe at least a first supply unit for providing the tobacco containing achemical solvent other than water comprises an impregnator where thetobacco is exposed to liquid or gaseous carbon dioxide.
 9. A systemaccording to claim 2, wherein the at least a second supply unit forproviding the tobacco containing water as a solvent comprises a silo forstoring the tobacco, the silo having an outlet, with a detangling unitfor detangling the shreds of tobacco being arranged in the silo.
 10. Asystem according to claim 9, wherein the detangling unit comprises aplurality of slowly rotating small doffers which are arrangedessentially over the entire width and height of the silo.
 11. A systemaccording to claim 1, wherein the tobacco expansion apparatus includes asupply of superheated steam or hot air and an entry section receivingtobacco from the first feed unit, the entry section comprising a Venturitype nozzle.
 12. A system according to claim 2, wherein the tobaccoexpansion apparatus includes a supply of superheated steam or hot airand an entry section receiving tobacco from the first feed unit and thesecond feed unit, the entry section comprising a Venturi type nozzle.13. A method of using the system of claim 1 to produce expanded tobacco,comprising impregnating tobacco in the first tobacco supply unit with achemical solvent other than water, supplying the impregnated tobacco viathe first feed unit to the tobacco expansion apparatus and expanding thetobacco in the tobacco expansion apparatus and removing expanded tobaccohaving a moisture content of about 2 to about 8 percent from the tobaccoexpansion apparatus.
 14. A method of using the system of claim 1 toproduce expanded tobacco, comprising impregnating tobacco in the secondtobacco supply unit with water, supplying the impregnated tobacco viathe second feed unit to the tobacco expansion apparatus and expandingthe tobacco in the tobacco expansion apparatus and removing expandedtobacco having a moisture content of about 2 to about 15 percent fromthe tobacco expansion apparatus.
 15. A method of using the system ofclaim 2 to produce expanded tobacco, comprising impregnating tobacco inthe first tobacco supply unit with a chemical solvent other than water,supplying the impregnated tobacco via the first feed unit to the tobaccoexpansion apparatus and expanding the tobacco in the tobacco expansionapparatus and removing expanded tobacco having a moisture content ofabout 2 to about 8 percent from the tobacco expansion apparatus, andimpregnating tobacco in the second tobacco supply unit with water,supplying the impregnated tobacco via the second feed unit to thetobacco expansion apparatus and expanding the tobacco in the tobaccoexpansion apparatus and removing expanded tobacco having a moisturecontent of about 2 to about 15 percent from the tobacco expansionapparatus.
 16. A method of using the system of claim 1 to produceexpanded tobacco, comprising impregnating tobacco in the first tobaccosupply unit with liquid or gaseous carbon dioxide, supplying theimpregnated tobacco via the first feed unit to the tobacco expansionapparatus and expanding the tobacco in the tobacco expansion apparatusand removing expanded tobacco having a moisture content of about 2 toabout 8 percent from the tobacco expansion apparatus.
 17. A method ofusing the system of claim 2 to produce expanded tobacco, comprisingimpregnating tobacco in the first tobacco supply unit with liquid orgaseous carbon dioxide, supplying the impregnated tobacco via the firstfeed unit to the tobacco expansion apparatus and expanding the tobaccoin the tobacco expansion apparatus and removing expanded tobacco havinga moisture content of about 2 to about 8 percent from the tobaccoexpansion apparatus, and impregnating tobacco in the second tobaccosupply unit with water, supplying the impregnated tobacco via the secondfeed unit to the tobacco expansion apparatus and expanding the tobaccoin the tobacco expansion apparatus and removing expanded tobacco havinga moisture content of about 2 to about 15 percent from the tobaccoexpansion apparatus.
 18. The method of claim 13, further comprisingdetangling the tobacco in a silo using doffers rotating at a speed ofbelow 100 rotations per minute arranged over the entire width and heightof the silo and feeding the detangled tobacco to the tobacco expansionapparatus.
 19. The method of claim 15, further comprising detangling thetobacco in a silo using doffers rotating at a speed of below 100rotations per minute arranged over the entire width and height of thesilo and feeding the detangled tobacco to the tobacco expansionapparatus.